[erlang-bugs] net_kernel hang, perhaps blocked by busy_dist_port race?

Scott Lystig Fritchie <>
Sun May 16 04:51:59 CEST 2010

New update: recipe to duplicate.


This recipe works for:

    Erlang/OTP R13B04 on Linux kernel
    Erlang/OTP R13B03 on same
    Erlang/OTP R13B02 on same
    Erlang/OTP R13B01 on same
    Erlang/OTP R12B-5 on same
    Erlang/OTP R11B-5 on same

The recipe requires a bit of luck and human intervention (pressing
Control-z at the right moment).  But I can get the error to happen
within a few minute's worth of trying.

Step #1, in terminal #1:

Run the following command:

    erl -sname foo1 -kernel net_ticktime 20 -eval 'register(foo, self()), [net_adm:ping() || _ <- lists:seq(1,100000)], erlang:display(done).'

Step #2, in terminal #2:

Run the following command:

    erl -sname bar1 -kernel net_ticktime 20 -eval 'F = fun(Ff) -> receive X -> io:format("Got msg ~p\n", [X]), Ff(Ff) end end, spawn(fun() -> io:format("I am: ~p\n", [self()]), erlang:system_monitor(self(), [busy_port, busy_dist_port]), net_kernel:monitor_nodes(true, [{node_type, visible}, nodedown_reason]), F(F) end), L1m = lists:seq(1,1000000), [{foo, } ! {bar, L1m} || _ <- lists:seq(1,555000)], erlang:display(done).'

As soon as you start seeting these messages in terminal #2:

    Got msg {monitor,<0.2.0>,busy_dist_port,#Port<0.98>}
    Got msg {monitor,<0.2.0>,busy_dist_port,#Port<0.98>}
    Got msg {monitor,<0.21.0>,busy_dist_port,#Port<0.98>}

... then you're ready for step #3.

NOTE: On my machine, pid <0.2.0> is the process that is executing the
code in the "-eval" flag, and pid <0.21.0> is the 'net_kernel' process.

NOTE: Using different releases of Erlang/OTP, the 'net_kernel' pid may
vary slightly, but it's in the 20's.

Step #3, in terminal #1:

When you see the {monitor,<0.21.0>,...} message in terminal #2, press
Control-Z in terminal #1.  If that message is the most recent/last
message, wait for 20 seconds or more.  You probably will not see a
'{nodedown,...}' message in terminal #2.

If you weren't fast or lucky enough, type "fg" here in terminal #1 and
then press Control-z again when you're feeling fast or lucky.  You're
sending big messages over to the terminal #1 node, so if you let this
run for too long, you'll run out of memory over there and crash.

Step #4, in terminal #3:

    erl -sname goofus1 -kernel net_ticktime 20 -remsh 

If you get an error in 10 seconds or less, congratulations!

    Erlang R13B04 (erts-5.7.5) [source] [smp:2:2] [rq:2] [async-threads:0] [hipe] [kernel-poll:false]
    *** ERROR: Shell process terminated! (^G to start new job) ***

Step #5, in terminal #2:

Press Control-g, then type the following at the prompts:

    --> s
    --> c 2
    ()1> process_info(whereis(net_kernel)).
    ()3> io:format("~s\n", [element(2,process_info(whereis(net_kernel), backtrace))]). 

In one of my attempts, I managed to get lucky and also managed to
block the 'global_name_server' process, <0.12.0>.

    ()2> process_info(pid(0,12,0)).        

    ()4> io:format("~s\n", [element(2,process_info(pid(0,12,0), backtrace))]).        
    Program counter: 0x08243388 (unknown function)
    CP: 0xb7704738 (global:do_monitor/1 + 172)
    arity = 1
    0xb748ab40 Return addr 0xb76fe8ec (global:insert_lock/4 + 100)
    y(0)     []
    y(1)     <4514.13.0>
    0xb748ab4c Return addr 0xb76fe704 (global:handle_set_lock/3 + 236)
    y(0)     []
    y(1)     []
    y(2)     {state,true,[],[],[{'',{1273,970221,319805},<0.61.0>}],[],'',<0.13.0>,<0.14.0>,<0.15.0>,no_trace,false}
    y(3)     [{<0.13.0>,<0.13.0>,#Ref<>}]
    y(4)     <4514.13.0>
    y(5)     {global,[<0.13.0>,<4514.13.0>]}
    y(6)     [<0.13.0>,<4514.13.0>]
    y(7)     global
    0xb748ab70 Return addr 0xb76fa488 (global:handle_call/3 + 184)
    0xb748ab74 Return addr 0xb769f8e4 (gen_server:handle_msg/5 + 152)
    0xb748ab78 Return addr 0xb7675258 (proc_lib:init_p_do_apply/3 + 28)
    y(0)     global
    y(1)     {state,true,[],[],[{'',{1273,970221,319805},<0.61.0>}],[],'',<0.13.0>,<0.14.0>,<0.15.0>,no_trace,false}
    y(2)     global_name_server
    y(3)     <0.10.0>
    y(4)     {set_lock,{global,[<0.13.0>,<4514.13.0>]}}
    y(5)     {<4514.13.0>,{#Ref<4514.0.0.20846>,''}}
    y(6)     Catch 0xb769f8e4 (gen_server:handle_msg/5 + 152)
    0xb748ab98 Return addr 0x0824852c (<terminate process normally>)
    y(0)     Catch 0xb7675268 (proc_lib:init_p_do_apply/3 + 44)

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